1. Field of the Invention
The present invention relates generally to a mobile communication system, and in particular, to an apparatus and method for generating a (n, 3) code and a (n, 4) code using simplex codes.
2. Description of the Related Art
In general, the CDMA (Code Division Multiple Access)-based future mobile telecommunication system known as “IMT 2000” transmits data for voice service and picture service, and control data necessary to provide those services. The ability to minimize errors generated during data transmission is crucial to improvement of service quality. For this purpose, error correcting codes are used to correct data bit errors. The purpose of using the error correcting is to minimize data bit rates in transmission data, and so, it is important to use optimal error correcting codes.
Linear codes are typically used as error correcting codes because performance analysis is a relatively simple process. The performance of the linear codes is measured by a Hamming distance distribution in the error correcting codewords. The Hamming distance is defined as the number of non-zero symbols in each codeword. For a codeword “0111”, its Hamming distance is 3. The smallest Hamming distance is called a minimum distance. As the minimum distance of codewords is increased, the error correction performance of the codewords is also increased. Accordingly, an optimal code is a codeword with a minimum distance, and thus, optimum error correction performance.
For details of a minimum distance between codes according to the input and output of binary linear codes to make the binary linear codes optimal for the length of code symbols encoded from an input information bit stream, see “An Updated Table of Minimum-Distance Bounds for Binary Linear Codes”, A. E. Brouwer and Tom Verhoeff, IEEE Transactions on Information Theory, Vol. 39, No. 2, March 1993.
In a (n, k) block code, n is the number of code symbols and k is the number of input information bits. The coding rate of the (n, k) block code is k/n.
If k is 3 or 4, a different encoder is used to generate the (n, 3) or (n, 4) code at a different coding rate. Thus, the use of multiple encoders for generating the (n, 3) code or (n, 4) code results in an increase in the structural complexity and increased size of the encoders and decoders.